RF amplifier circuits are old and well known in the art and are generally used in transmitter/receiver circuits. A unique RF amplifier circuit has been disclosed in commonly assigned U.S. Pat. No. 5,357,206, incorporated by reference herein in its entirety, as a novel RF receiver that utilizes sequential RF amplifiers. A further improvement of that invention is disclosed in commonly assigned U.S. Pat. No. 5,787,117, also incorporated herein by reference in its entirety, and that discloses a transceiver created by using the novel sequential RF amplifier circuits. These novel inventions have met with great success.
Such development has been used to implement a single-channel SRD radio with good performance and with a very low power budget. Single-channel radios currently address a significant number of short range device (SRD) applications including remote keyless entry (RKE), tire pressure monitoring (TPM), gate/door control, wireless security systems, radio frequency identification (RFID) tags, sports/medical telemetry, and many meter reading applications including automatic meter reading (AMR), etc. These circuits have great value because they are reliable, economical, use low power, and have significant advantages over the prior art systems.
However, some meter reading systems, all cordless phones, most PDA/laptop network radios, and a number of other applications utilize MULTI-CHANNEL, or, more generally, multi-session unlicensed radios. Multi-session radios avoid or minimize in-band interference where several uncoordinated radio systems are operating in the same vicinity. The two most commonly used multi-session strategies are frequency channelization and spread spectrum coding. Most unlicensed radio systems used with PC technology operate in the 2.4 GHz band, which is the lowest industrial, scientific, and medical (ISM) frequency band above 300 MHz that is available in all regions. Operation in the 2.4 GHz range is also particularly interesting for Japan where the alternative is very low power operation under Bijaku regulations.
It would be advantageous to be able to utilize the sequential amplifier technology to develop a frequency agile RF system that could use multi-channel or frequency hopping operation.